A young man from rural Brazil is visiting family in the United States when he becomes ill with muscle pains, high fever, and hepatosplenomegaly. A blood sample taken in the emergency department reveals the following organism at 1000$\times$. The most likely identification of this organism is

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The symptoms of muscle pains, high fever, and hepatosplenomegaly suggest a parasitic infection, and the high blood parasite count (1000F1F1F1S1F1F1F10) suggests a hemoflagellate such as Trypanosoma cruzi, which causes Chagas disease. Leishmania donovani and Babesia microti are also parasitic protozoa that can cause similar symptoms but are not hemoflagellates. Plasmodium falciparum can cause fever and hepatosplenomegaly but usually presents with anemia and would have a different appearance on blood smear.

A Young Man from Rural Brazil Is Visiting Family in the United